Update a field during upload

how can i update a field during an upload using a sharepoint designer. let say i upload a csv file in document library and i want update a field value based on csv value. consider that we don't know the field name. Is there any spservice example code that
i can refer to. and which page should i implement that code Pls help thanks in advance

I had this same need a few years ago which led me to create a Widget library. Take a look at SPControlUpload of SPWidgets - here:
http://purtuga.github.io/SPWidgets/
The widget allows you to upload a file to a document library and has a way for you to "catch" the Check In form and populate it with data. Or: update the file record in the doc lib. via UpdateListItems after it's uploaded.